Page 33 - Focus SPM KSSM F4 2020 - Chemistry

Chemistry Form 4 Answers

The density of the mixture • Barium sulphate salt is move throughout the liquid. They
is calculated as follows: used to check our digestive have low energy content.
Density = system using X-ray. Patients Q2 (a) 0°C
Mass of mixture (g) will have a drink of the salt (b) This is because the heat energy
Volume of mixture (cm ) before X-ray images are absorbed by the molecules of ice
3
[1] taken. [1] is used to overcome the forces
• The constant variables (any 10 examples of between molecules so that ice
are pure water and type other chemicals are also can turn into water.
of salt used. [1] accepted) (c)
• So, pure water is used 10 Temperature (°C)
every time. Only one type (b) Hypothesis : Painting prevents
of salt is used throughout rusting of iron [1] 120
the experiment, for Variables: 100
example sodium chloride. Manipulated: Presence of a
[1] layer of paint on iron [1]
6
Responding: Rusting of iron [1]
Section C Constant: Presence of water [1] 15 S
Procedure: 0 Q
3. (a) • We use various chemicals –3 P R
in many aspects of our Time (min)
lives such as in foods,
agriculture, industries and Checkpoint
medicine. Water pipes 2.2
• For example, we use Painted Q1 (a) Hydrogen atom has 1 proton
sodium chloride and iron nail with relative charge +1 and 1
monosodium glutamate [1] electron with relative charge -1.
Hence the net charge of H atom
(MSG) as flavourings in our 1) Two iron nails are cleaned is (+1) + (-1) = 0
dishes. [1] with sand paper. [1] (b) All the protons and neutrons
• Sucrose or sugar is used 2) One iron nail is painted with of an atom are found in the
in various foods such a layer of paint and left to nucleus.
as desserts, cakes and dry. [1] A proton or neutron is
delicacies. [1] 3) Both nails are placed approximately 2000 times
• Acetic acid (ethanoic acid) in separate test tubes heavier than an electron.
is used as vinegar to pickle containing tap water and are Q2 An atom is a discrete particle, very
foods. [1] left aside for three days. [1] small and indivisible.
• In agriculture, ammonia is Observation: Q3 (a) Electron
The painted iron nail does not
used to make fertilisers for rust while non-painted iron nail (b) Thomson’s atom is a positively-
crops. [1] rusts. [1] charged sphere embedded with
• Slaked lime (calcium Conclusion: Q4 • electrons.
Rutherford discovered the proton
hydroxide) is used to treat Painting prevents rusting of iron. which is positively charged.
acidic soil. [1] [1] • He proposed the atomic model
• Hydrocarbons from 10 which consists of a positively-
petroleum are separated charged nucleus and negatively-
by fractional distillation and charged electrons orbiting
are important fuels. For Chapter Matter and the Atomic around the nucleus.
example, petrol and diesel 2 Structure • He stated that the mass of an
are fuels for vehicles. [1] atom is concentrated in the
• We also use various nucleus.
petrochemical products Checkpoint 2.1 Q5 • Bohr introduced the concept of
such as plastics, detergents, Q1 • The particles in a gas are very shells.
synthetic textiles and far apart from each other and in • He stated that electrons orbit the
synthetic rubber. [1] random motion. The particles can nucleus in fixed shells.
• Metals such as copper, zinc, vibrate, rotate and move freely. Q6 (a) Neutron
aluminium and iron are used They have high energy content. (b) • Proton and neutron are
in various machines and • When the gas is cooled, the found in the nucleus.
important metal equipment particles of the gas lose energy • Neutrons contribute half the
in industries. [1] and move slower. overall mass of an atom.
• Various slats are used to • Eventually, the gas changes into
treat malnutrition diseases a liquid. The particles of the liquid Checkpoint 2.3
such as iron(II) sulphate is are packed closely together but
used to treat lack of iron in not in an orderly arrangement. The Q1 (a) Proton number = 9
anaemic patients. [1] particles can vibrate, rotate and Nucleon number = 19

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10 ANSWER FOCUS KIMIA F4 SPM.indd 259 27/02/2020 11:29 AM